I have a 95 Corvette with battery issues. Basically, if the car sits more than 24 hours the battery will be dead. Since I do not daily drive the car it sits for more than 24 hours a lot. I think my screw up caused this so let me tell you what happened so maybe there is someone on here who knows what the fix might be. I did not winterize my car so I usually took it out for a good drive every weekend during the winter as weather permitted. I got lazy around February and let the car sit in my garage for a month without running it. I went to start it and the battery was dead. Not a surprise as a month in cold weather is long enough to drain a car battery. I have a Lincoln Navigator so I went to jump the Corvette. Here is where I screwed up. The Navigator has a thick red wire attached to one of the battery terminal's so I assumed that was positive as I have always associated red with positive and black with negative or ground. Unfortunately that red wire was in fact going to my Navigators ground terminal so I had the jumper cables hooked up wrong. Navigator's positive was hooked to Corvettes negative and Navigator's negative was hooked up to the Corvette's positive.

I didn't realize this right away so I sat down inside the Corvettes driver seat and was waiting for a few to let the battery build a charge. That's when I started smelling a burning smell and saw smoke. I jumped out of the car and unhooked the cables. After realizing what I had done, I cursed myself for being so stupid. The Navigator was fine. The Corvette smelled like burnt electronics and the battery was toast. I went to Walmart and bought a new battery for the Corvette. It started up fine and all gauges were working so it seemed like all was ok. This was on a Saturday afternoon. I tried to start the Corvette on Monday afternoon (less than 48 hours later) and the new battery was dead. Not click, click, click dead but so dead that the interior light wouldn't even come on and the ignition chime from the key didn't sound. I jumped the car correctly this time and it started. I drove it around for an hour and when I shut it off it did restart strong so I hoped all was good. The next day the battery was totally dead again. I took the battery back to Walmart and they tested it overnight. The result was it would only hold a minimal charge so they replace it for me with another new battery.

I drove the car for a bit with the second new battery and then car sat in my garage for 3.5 days during warm weather. I went to start it and the second new battery was totally dead. Again so dead that no lights or chimes can come on or sound. Either I am extremely unlucky and walmart sold me two defective new batteries or my jump fiasco did more than I thought. That burnt smell stayed in the car for a few days too BTW. With the whole pandemic stuff going on I have not taken the car to a mechanic yet but unless it's something I can fix myself then I will have to.

Any idea what I might have fried that causes my car to drain the battery when it's sitting? It seems like something is drawing power like if you left your interior light on by accident. I have to unhook my battery if I want it to hold a charge from one weekend to the next.

 

You might want to disconnect the alternator completely (be careful the hot lead doesn't touch a ground) and see if the battery holds a charge. It could be possible that the regulator or diodes were damaged and it's draining through the alternator. Just a thought. You might end up performing a parasitic draw test.

 

There many possibilities, but I feel a good place to start is the alternator you may have cooked the Diode bridge. Easy test with the car at rest charged battery nothing on or running disconnect alternator if you get a large spark may be the problem. Leave the alternator unplugged overnight and see if it is dead in morning

 

Thanks for the replies. My mechanical background is pretty decent for a novice. I have replaced multiple alternator's, starter's, batteries, brake pads, rotors, upper control arms, lower ball joints. I have also done a lot of my own modding such as installing Cam's, LT headers, CAI's, underdrive pulley and even a N20 kit once. That said, I have no experience with the electrical side of cars other than disconnecting the battery to change starters or alternators and running wires for the N20 kit.

I will be more than happy to just change out the alternator with a new one. Even if that doesn't fix the issue, it's a cheap enough part that doesn't take long to install. I will also check the diode for the power seat harness. Thank you for the input.

 

I don't understand. You presented a problem, and several people have given you good advice, and yet you choose to ignore that good advice? Why even bother trying to help you??

 

You need to identify the circuit that is leading to the parasitic draw on your battery, you identified that this was happening with the key on the off position, so it has to be a circuit that is live with the key off, do you have a multimeter, if you do you need to set in to amps and connect it in series between the positive battery cable and the positive terminal on the battery, this is identify what amps the car is pulling with the key in the off position, firstly disconnect the under hood lights, if you have a door open this is still show a slight current draw, then whilst checking the multimeter pull one fuse at a time until you eliminate the greatest draw, this will be the circuit that is killing your battery, it is most likely a relay or switch stuck in the open position

Remember you have a 60 amp/HR battery, so a 2 amp draw will flatten a battery in 30 hrs. .

 

Drive it to advanced auto and get an electrical system check for free

 

Alternator was the most popular response so I figured I would take that advice and start there. It's a $60 part and the current one is very old so I really don't mind changing it regardless of whether it fixes this issue or not. Worst case is I am preventing a problem down the road. If that fixes this problem then great! If it doesn't, I plan to follow other suggestions in this thread such as testing the power sear harness as Ihatebarking dogs suggested and if that fails then I will move onto the multimeter test suggestion from braeburn22. Between all that great advice, I am hopeful that I will have found and fixed the issue.

I am grateful for all the good advice people have given me and plan to use the tips here one at a time, starting with the alternator. The real question is why would you bother to come into this thread just to be condescending?

BTW, I plan to work on the car this weekend and will update this thread with how it all goes. Thank you all again for the input.

 

I concur with prior responses. You can always pull fuses to all non essential accessories to find current draw. I start at basics...is any of you interior lights/etc switched always on?

 

No. Everything looks and sounds normal when I shutoff the car and remove the key. Alternator will be here tomorrow and I will install it on Friday. I do have a multimeter so I will check the power draw after the new alternator is in. If one still exists then I will start pulling the fuses one at a time until I find the one associated with the draw. Hopefully, I'll have this all squared away by the end of the weekend.

Thanks.

 

There is a tester called amp hound for finding parisite current drain. You don't want to be removing fuses especially on newer vehicles in your search.
One if the tester lenders car parts store has it to borrow.

 

jumper cables are dangerous. besides the 99% chance your destroying electrical systems. jumper cables belong back in 1970. over in the c5 c6 sections i see guys wrecking body control modules ect all the time from dead and or low voltage batteries. High amps draw from low voltage while trying to start a car stresses out everything. either charge your battery 100% or buy a new one. throw the cables in the garbage.

 

Here is where I am at. I replaced the alternator so that's done. I had walmart charge my battery for a couple of hours to verify that it is good and it was. I have an everstart digital multimeter so I put to batt and 12V just to see where the battery was. It read 12.29V. The car starts up just fine. Then I took off the positive terminal lead and reset the muntimeter to A and set ithe dial to 10A. In DC mode I touched the positive cable to the positive terminal on the battery. Nothing. No reading at all (0.00). I replaced the positive terminal to the battery and removed the negative. Touching the negative cable to the negative terminal on the battery I also got nothing, 0.00.

That's with the multimeters red cable plugged into the 10A port on the multimeter. If I move it to the VmA port then I do get a small reading of 0.08 but think think that is just a continuity test. Not sure though.

So for now all I can do is leave the battery hooked up and test the battery in the morning to see how much of the 12.29V got drained.

 

.08 amps is 80 mA, your battery should last quite a few days without starting the car now.

 

Well I'm back to square one. The battery was completely dead with the car sitting for just 24 hours. I'm going to return the multimeter I bought and buy a better one because I am dead in the water if I can't get an amp reading to troubleshoot with. I will also have to pick up a battery charger, Every time I set up the multimeter for amps (highest setting was 10) it would read 0.00 without even a flicker. There was obviously an amp draw there so it should have shown me a number and probably a big one.

 

Just a thought on you not getting a reading you have to be a little careful, I know with my meter if I put to 10 amps bridge and between POS cable and POS post without a jumper lead until the Interior lights go off it blows the fuse in the meter

 

That sucks. But I bought the multimeter at walmart last weekend so they will exchange it no questions asked. I've been watching youtube videos on parasitic draw tests and my battery might not have been charged enough to do the test properly. Mine read 12.39 but every video says make sure your battery reads 12.6 or more before proceeding. I guess I need to replace the multimeter and charge the battery until it's 12.6+ V and I will make damn sure the car is in sleep mode before I proceed and try this test again.

Thanks.

 

If your battery is off by .20 I think a parasitic draw test would still reflect a drop in power once you pull that fuse. Think about it, if you pull out the fuse at 12.6V or 12.4V it will still drop. Do the draw test and see if anything stands out to you. If nothing does and you want to re-test with the battery at full power then go for that.

Definitely just don't go and swap parts, do the tests first.

 

How are you hooking up the Amp meter? I wasn't sure from your post.
O'Reilly auto parts should have a "Amp hound ' to borrow to check for a draw with.

 

Update:

I went out and bought a battery charger. A spent a little more money to get a decent one that includes a battery voltage test, alternator test and jump start. I also exchanged my multimeter for another one since it was not registering amps. The battery charger says it cannot charge or jump a battery that is under 2V and mine was completely dead. So I had to hold my breath and jump start the car to build up a little juice in the battery so that the battery charger could take it from there. I got to say that I was shocked at what happened. Once I got the car started, I unhooked the jumper cables and let the car idle for 3-5 minutes, I didn't drive anywhere, I didn't rev the engine. Just let it idle for 3-5 minutes.Then I shut it down and checked the voltage of the battery. I was hoping to see 3-8V. The battery was at 12.5V after just a few minutes of idle. This really surprised me because the alternator seems weak. The car tested 13.9 V with the engine running but I read that 14.5 is what you want to see.

Anyway, I hooked up the battery charger and let it charge the battery to 100% full which was something like 13.6 V I think. I removed the negative cable to my battery and set the new muntimeter to amps. It showed a .5 amp draw while the car was in sleep mode. This was lower than what I expected. I was thinking I had a 2-3 amp draw. Still half an amp is enough to drain a battery so I went to the fuse panel. I remember someone in this thread mentioned that the power seat may have been what the burning smell was so I wanted to check that fuse first. There are two large fuses to the right of all the normal fuses. One is for the power seat. I pulled that one first and noticed it felt warm even though I had not adjusted either seat in over a year. With that fuse out, I checked the multimeter again and the draw had dropped from .5 to .07.

I closed everything up and let the car sit for 36 hours. I checked the battery for volts and found it was at 12.5 so it had dropped only 1V in a day and a half. I started the car and it started right up and I took it for a drive. I work a four day work week away from home so I won't be back there until this Friday. It will have sat for a full 4 days at that point but I fully expect it to have enough juice to start up based on what happened over the weekend. I don't ever need to adjust either seat so it's no big deal to just leave that fuse out.

Thanks you all again for your advice and input.